This invention relates to electrical power generating plant.
There is a growing need at the present time for the use of clean fuels in electrical generating plant. This need arises out of the growing concern over the problems of atmospheric pollution, caused primarily by the burning of dirty fuels which are relatively abundant. Sources of fuel having an acceptable degree of cleanliness are available; such fuel sources include, for example, coal gasifier plants and synthetic gas production plants. However, such clean fuel sources involve a very high capital cost, and would be extremely uneconomical to operate except when working at full capacity. Apart from cost considerations, such clean fuel sources cannot easily be regulated to meet the requirements of a variable demand for energy.
These problems associated with presently available clean fuel sources are particularly serious if the fuel sources are to be used with electrical power generating plant, for if the generating plant is required to meet a variable load demand, the fuel source as well as the components of the plant itself must be designed to meet maximum load conditions and the operating cost of the system in off-peak periods (represented by the ratio of the capital cost to the useful power output) may well be prohibitive.
It is an object of the present invention to provide an improved power generating plant in which useful energy is derived from the fuel source continuously despite variations in the load demand on the system.
According to the invention there is provided an electrical generating plant comprising a generator which is driven, during on-load periods, by a gas turbine; the gas turbine operates continuously and is powered by a continuous supply of fuel gas from a suitable fuel source and compressed air from an air storage reservoir; the reservoir is recharged periodically from an air compressor driven by the gas turbine during off-load periods only. The air storage reservoir thus serves to store energy supplied by the system during off-load periods and to return that energy to the system during on-load periods, in which the air compressor is inoperative and places no load on the gas turbine.
In one embodiment of the invention, the generator is adapted to operate as a motor during off-load periods, and so to assist the gas turbine. In this case the motor-generator is powered from an auxiliary generator driven by a steam turbine incorporated in the system. In this way the on-load periods of the system can be extended.